a. Field of the Invention
This invention relates to a multiple-glazed window containing an integral assembly for controlling the amount of daylight passing though the window into a room. In particular, the invention relates to a window having a peripheral frame enclosing inside and outside glass panes that are substantially parallel and define a space between them which is preferably sealed and in which the light-control assembly is mounted.
b. Background Art
Double-pane windows containing motorized venetian blinds as light-control assemblies have been described in U.S. Pat. Nos. 4,723,586 and 4,979,552. Such windows have satisfied most light-control requirements. In addition, the mere positioning of a venetian blind within the space between two glass panes in a window has long been known to reduce heat losses by radiation through the window to an extent approaching those of windows with triple panes.
Notwithstanding this, the increased use of computer monitors in office buildings has presented additional demands on windows and their associated light-control assemblies for providing protection against the glare from sunlight, without totally eliminating daylight illumination within such buildings. Blocking such glare by closing the window blinds has often diminished the level of illumination in offices below acceptable limits, but increasing the use of artificial illumination, such as electric lighting, has also been objectionable from an environmental point of view.
Anti-glare venetian blinds have also been previously described. For example, in European patent 0,303,107, an anti-glare venetian blind is provided with slats: which are upwardly concave, which have their inner longitudinal edges (facing towards the room) as high or higher than their outer longitudinal edges (facing away from the room), which are mirrored on at least their topsides and retro-reflecting on their undersides, and the spacing and position of which are so selected that the light passes through them mostly into an angular region above the horizon. In European patent application 0,606,543, an anti-glare blind is provided with slats which are: upwardly concave, mirrored on their topsides and at least partially perforated. Although these blinds appear to be able to guide light towards the ceiling of a room and avoid glare, they are not adapted to allow some sunlight to enter the rest of a room. In this regard, it would be desirable, on sunny days, to be able to block or inhibit heat and glare from entering the rest of the room, without blocking daylight illumination entirely from the rest of the room.
For this reason, there has been a continuing interest in eliminating glare and sunlight from the lower portions of office windows while redirecting light from the upper portions of office windows within offices. It is therefore an object of this invention to provide an improved multiple-glazed window with an integral light-control assembly.
In accordance with this invention, a double-pane window is provided, containing, within a peripheral frame, a light-control assembly that includes:
i) an upper section which is adapted to redirect light entering the window through the outside pane so that the light exits the window through the inside pane; and
ii) a lower section which is adapted to reduce or eliminate light entering the window through the outside pane from exiting the window through the inside pane. Preferably, the light passing through the upper section of the window can be reflected upwardly, against a ceiling surface of the interior of a room, to provide additional illumination. In the lower section of the window, sunlight and glare from the outside, which might otherwise disturb the occupants of the room, can be substantially reduced or eliminated as desired without losing altogether the benefits of daylight illumination.
Advantageously the upper and lower sections each comprise a venetian blind assembly provided with a plurality of substantially parallel laterally-extending elongate slats, the slats of at least the lower section being pivotable about their laterally-extending axes. Such an assembly allows the use of standard components from existing double-pane windows containing enclosed venetian blinds such as are disclosed in U.S. Pat. No. 4,723,586.
Desirably, the lower section of the light-control assembly is adjustable independently of the upper section. This permits the assembly to be used to optimize light control under different conditions.
The slats of at least the upper section of the light-control assembly preferably have a highly reflective upper surface for improved control of daylight which these slats redirect through the window. For the same purpose and advantageously in combination therewith, the slats of at least the upper section can be perforated or partly translucent.
Further enhancement of light distribution with the window of the invention can be obtained by giving the slats of the upper section a cross-section, as taken transversely (i.e., from the outside to the inside of the window), that includes a concave surface facing upwardly. In certain embodiments of the invention, each of the upwardly concave slats of the upper section preferably has a mirrored top surface and a retro-reflective bottom surface. In other embodiments, the upwardly concave slats of the upper section preferably have a mirrored top surface and are wholly or partially perforated.
In addition, heat losses by radiation through the window of this invention, particularly in the winter, can be further substantially reduced by providing the surface on the inside- and/or outside-facing surfaces of preferably all of the slats with an emission coefficient lower than 0.5, and preferably lower than 0.3, for radiation with a wavelength larger than 1.5 micrometer. In this regard, advantageous are aluminium slats coated with a very thin zinc chromate layer, such as are described in British patent 1,536,600.
Although each slat of the light-control assembly in accordance with this invention can be individually suspended from pivots on laterally opposite sides of the window frame, it is preferred that the slats be tiltably suspended from laterally-spaced tilt cords. In this regard, the slats of the lower section of the light control assembly may be tiltably suspended from laterally-spaced tilt cords and the slats of the upper section be non-tiltably fixed in a position re-directing light upwardly towards the ceiling of the room.
Preferably an electric motor is used to adjust at least the slats of the lower section of the light-control assembly. A suitable electric motor is described in U.S. Pat. No. 4,979,552 and is preferably hermetically sealed in the space between the windowpanes. The use of such an electric motor is particularly advantageous when movement of the light-control assembly is to be adjusted with a microprocessor control so as to allow optimal light regulation under varying conditions without requiring the intervention of the room occupants.
In one embodiment of this invention, the top of the lower section is suspended from a laterally-extending intermediate bar, beneath the upper section. Such an arrangement allows an increased number of existing components of known double-pane windows containing venetian blinds to be used and also allows the upper and lower sections to be mounted in the window in essentially the same manner. Advantageously, the intermediate bar is suspended only at its lateral edges from laterally opposite sides of the frame, using a T-shaped connector at one lateral edge and an electric motor for the lower section as a connector at the other lateral edge.
The window of the invention is substantially vertical. Normally it will be truly vertical but it may be mounted in a slanted position in which case the plane of its light-control assembly is advantageously positioned closer to the upper glass pane of the window, as so mounted. In this regard, it is especially advantageous that the attachment of the upper and lower sections of the light-control assembly to the intermediate bar be positioned closer to the upper glass pane to compensate for any sagging of the light-control assembly within the slanted window, and it is particularly advantageous that the upper end of the upper section and the lower end of the lower section also be positioned closer to the upper glass pane to compensate for any sagging of the light-control assembly within the slanted window.